Safety device for a basket



June 22, 1965 Filed Dec. 2 1963 L. M. HOARD SAFETY DEVICE FOR A BASKET 2 Sheets-Sheet l FIE Z INVENTOR.

LEE M. l-IOA RD ATTORNEYS J1me 1965 L. M. HOARD 3,190,391

SAFETY DEVICE FOR A BASKET Filed Dec. 2 1963 2 Sheets-Sheet 2.

l O0 0 o0 0 0 INVENTOR. LEE M. H OARD .W WMM ATTORNEYS United States Patent 3,190,391 SAFETY DEVICE FOR A BASKET Lee M. Hoard, San Lorenzo, Calif, assignor to Utility Body Company, a corporation of California Filed Dec. 2, 1963, Ser. No. 328,784 10 Claims. (Ci. 182-2) This is a continuation-in-part of application Serial No. 251,845 filed January 16, 1963, now abandoned.

This invention relates in general to a safety device and more particularly to a safety device for a platform or basket which is pivoted at one side or edge thereof or at a point adjacent the bottom and which may therefore be subject to sudden and undesired pivoting on failure of its control mechanism.

Ladders or booms mounted so that they may be raised or lowered and which support work platforms or baskets for use at elevated locations such as for power line work, tree trimming and the like, are Well known. One form utilizes a work platform or basket which is pivoted at the side or base thereof. This arrangement has various advantages which are well understood to those skilled in the art and need not be detailed here. Because the tendency of such platforms or baskets is to pivot under the infiuence of gravity so that ultimately the base or platform will rest more or less vertically, it is necessary to provide means for maintaining such platforms in a horizontal position. This involves continuously changing the angle between the horizontal platform and the boom upon which it is mounted as the boom is raised or lowered; an hydraulic cylinder assembly pivoted at one end thereof to the boom and at the other end thereof to the platform represents a convenient leveling mechanism. Automatic control means are provided, as is well understood, for retracting the piston rod as the boom is lowered and for extending the piston rod as the boom is raised.

It is obvious that in the event of failure of any of the links between the leveling cylinder assembly and the boom or work platform, or in the event of failure of the associated hydraulic system, the work platform would rotate about its pivot point and pitch the workman, tools, etc. to the ground.

It is an object of this invention to provide a safety ap paratus for a work platform or basket generally of the type aforementioned.

It is a further object of this invention to provide a safety device which will prevent a Work platform or basket from pivoting freely on loss of power to or failure of the hydraulic cylinder which is relied upon to level the platform.

Other objects and advantages of this invention, if not specifically set forth, will become apparent during the course of the description which follows.

In the drawings:

FIGURE 1 is a schematic fragmentary side elevation of a supporting boom, basket and associated leveling and safety apparatus.

FIGURE 2 is a fragmentary side elevational view showing a boom and basket in different relative positions which omits the schematic representation of the safety features.

FIGURE 3 is a view on the line 33 of FIGURE 1 showing the relationship of the various parts.

FIGURE 4 is an enlarged sectional view of the valve which forms a portion of the safety apparatus.

/ FIGURE 5 is a fragmentary side elevation of another embodiment of the invention wherein the platform is pivoted to the supporting boom at a point beneath the platform and located intermediate its ends so that the platform is susceptible to tipping in either direction on failure of the control mechanism.

FIGURE 6 is a schematic representation of the safety mechanism of FIGURE 5.

Generally, this invention comprises a safety apparatus for a platform hinged at one edge or along the bottom thereof to a boom capable of being angularly raised and lowered. There is provided a first hydraulic cylinderpiston-piston rod assembly pivoted at one end thereof to the boom and at the other end thereof to the platform. The assembly is pivoted to the platform whereby to provide means for varying the angle between the boom and the platform and for leveling the platform. There is also provided means for preventing a sudden change in the angle between the boom and platform on failure of the first hydraulic cylinder-piston-piston rod assembly. This means consists of a second hydraulic cylinder assembly secured at one end thereof to the boom and at the other end thereof to the platform, the second cylinder assembly just mentioned being pivoted to the boom or platform at a point spaced from the point at which the platform itself is hinged to the boom. There is also provided an hydraulic fluid line connecting the piston side of the. cylinder of the second assembly aforementioned and the rod side of the cylinder of the assembly aforementioned or, more generally expressed, joining the two ends of the cylinder on either side of the piston. In this line is a counterbalance valve. A counterbalance valve may be defined as an adjustable relief valve and a free-flow check valve assembled together in one body in such a way as to allow essentially free flow through the valve in one direction and a relief valve action when the flow is in the other direction. The counterbalance valve is set to prevent flow of fluid and therefore tipping of the basket except when there is a positive force applied to the basket which would create a pressure within the safety cylinder sufficient to overbalance the setting of the counterbalance valve. The source of this positive force is the first or leveling'cylinder assembly. If there is a failure of any kind in the leveling cylinder or of the hydraulic circuit of the leveling cylinder itself, there would be no positive force available to overbalance the counterbalance valve; therefore, the basket would remain in the position at which failure of the valve or its hydraulic system occurred.

Referring now to the drawings wherein like characters refer to like parts throughout, there is shown in FIG- URES 1-4 a boom 10 which may or may not be extensible, as desired. Pivoted at 12 is the basket 14 which includes platform portion 16 and side walls 18. The basket is conventionally made of :Fiberglas. The first or leveling hydraulic cylinder-piston-piston rod assembly 20 is pivoted at one end thereof at point 22 to boss 24 secured to boom 10 and at the other end thereof at point 26 to boss 28, in turn secured to a point on one wall of the basket, which point is vertically displaced from pivot 12. The second or safety hydraulic cylinder-piston-piston rod assembly 30 is pivoted at 32 to the distal end of the boom 10 and pivoted at point 34 to the boss 35 which is vertically spaced on basket 14 from pivot 12.

The assembly 30 has oil on either side of the piston and means are provided for transferring oil from the cylinder side of the piston to the rod side or vice versa. The means consist of fluid line 36 having therein the relief in cross section in FIGURE 4. In communication with the fluid line 36 by means of line'40 is the reservoir4-2. which serves to provide fluid for the piston side ofthe safety cylinder in excess of the fluid forced from the rod side of the safety cylinder at such time as the piston is moved to extend the piston rod. Obviously, because of ing oil to the piston side of safety cylinder assembly 30 as shown in FIGURE 1 and at about two atmospheres pressure when serving as a reservoir for a maximum quantity of oil and when the condition represented in FIG- URE 2 obtains;

A typical valve incorporatinga relief valve and a check:

valve and gene-rally designated, a counterbalance valve is 36. Compression spring 56 is held in place by means of The volumes oneither side of piston (128 are filled with hydraulic fluid and the lines 142 and 144 permit flow of such fluid from one side of the cylinder to the other, such flow, in one direction, always being through a single combination of a reliefvalve and a check valve in series therewith, e.g. through valves l 32 and .138 when the fluid flows from the left side to the right, as seen in FIGURE 6.

' In the operation of the structure of FIGURES 1-4, as the boom'10 is raised, the rod of the safety cylinder is extended. The cylinder assembly 20 exerts a pressure in excess of that of spring 7.6and fluid moves from the rod side of assemblyv 30 through passage 66, past the retracted sleeve 70, and through port 52 and line 36, thence to the piston side of the cylinder assembly 30. Additional oil is always provided from reservoir 42. As the boom 10 is lowered, the safety cylinder retracts and oil on the piston side of the cylinder 30 flows readily throughthe valve after unseating ball 6-2. In the event of 'a failure of the leveling cylinder 20, of one of the bosses 2 4 or 28, or of either of the pins 22 or 26, sleeve 70 will not be retracted and they valve 38 will retain the oil in the rod shown in section in FIGURE. 4. The valve housing 50 has inlet port =52 and return port 54, the former being connected to the piston side of piston assembly 30 via line "2'5 cylindrical counter-bored plug 58, O-ring ,60 assures a tight seal against fluid leaks, The spring 56 bears against ball 62 which is seated at the mouth of passage 64. The 7 "spring is suitably sized so that'ball 62 will'moye' against the spring tension on application of a low pressure, cg.

one p.s.i. This provides for the return of fluid from the piston side of the cylinder assembly 30 to the rod side when the boom 10 is being lowered, and the platform or basket is pivoting upwardly relative thereto. On the application of any positive pressure from the direction'of port 54, the ball tends to seat more securely. Movement of fluid through passages 66 and 68 is normally'blocked'by cylindrical hollow sleeve 70 which is slida bly mounted therein and provided with suitable sealing rings 72and 74.

As the boom 10 iselevated, fluid must be removed from the rod side ofthe cylinder assembly 30 and passedvto the piston side. Spring '76 isheld in place by plug 78 sle'eve70 so as to obstruct the passage of fluid from the rod side of safety assembly 30. Pressure in excess of the spring setting applied through passage 66 forces the sleeve toward'the bottom in FIGURE 4 whereby to open the entire route for hydraulic fluid extending from return port 54 through passage 66, passage 68 and out inlet port 52 to the piston side of assembly 30. I a

An alternative double-acting safetyapparatus is shown 7 covered by cap 77 and exerts a pressure on the hollow. I

side of the safety cylinder assembly .30. This prevents further extension of the rod' thereof, holdingthe basket in the position in which it was at the time of the aforementioned failure. With a spring 76 suitably sized to require a pressure of 700 psi. to retract sleeve 70, and

with an average load creating a pressure of 450 pounds, it will'be possible for the basket to be slowly tipped by the operator jumping up and down to overcome the setting; Otherwise, the basket will be retained in the orientation wherethe failure occurred.

In the operation of 'the structures of FIGURES 5 and 6, as the boomis raised, the piston of the safety cylinder 130 moves/to the left, given the. relationship of the viewer and the platform presented by FIGURES 5 and 6. That is, since sprocket 102 is keyed to the end of the boom and thus moves counter-clockwise with respect to the work platform 106, the chain 122 is moved in a counter-clockwise direction, thereby pulling the piston 128 to the left and forcing hydraulic fluid out of the left side'of thecylinder 130.- The setting of the relief valve 132, in a preferred'e'mbodiment, is at 1800 p.s.i., so that a 2000' lb. or lesser weight offset somewhat from the center of the platform 106 would be insuflicient to tioned, the platform would tend to rotate'about pivot in FIGURES 5 and 6 wherein a boom .100 hasa sprocket 102 keyed thereto. Pivoted about point 103st the center of the sprocket is the generally V-shaped framework 104 which supports the horizontal platformframe member 106, in turn supporting side railing assembly 2108. Asin the caseof structures *1-4, 'a leveling cylinder 1 10 is supported by the boom. Specifically, the cylinder 110 with its piston rod 112 is pivoted at one end thereof to the parallel ears 114 which are in a fixed orientation relative to the boom. The piston rod 112 is pivoted to the under side of the platform at point 116. A pair of idler sprockets 1118 and .120 "serve, with fixed sprocket .102, to provide a complete support for the link chain 122. Ends of the point 103. Assumingthat the platform is unweighted in the directiontoca-use it to rotate clockwise, chain 122 will pull piston 128 to the left relative to the platform. Sprocket 102 is fixed and this sprocket in turn fixes the chain. Since,. as seen in FIGURE .6, the only route by Y which hydraulicfluid maybe expelled from the left side chain are secured respectively to piston rods 124 and 12-6,

in turn secured on opposite sides of piston 1 28 which slides in cylinder 130. A system somewhat similar to that of the structure of FIGURES 1-4p1'ovides the safety feature,

including, asshown in the schematic view of FIGURE/6, I

a pair of ,relief valves, respectively 132 and 134, anda pair'of check valves 1 36 and Y138, together with a reservoir or accumulator140. Each valve assembly consists a.

'of a relief valve 132 or 13 4 with its respective parallel of cylinder 30 is through relief valve 1 32,"clockwise rotation of the entire pla'tform'is' impossible unless sufficient forceis applied to overcome the'setting of the valve, as by the larger'hydraulic system incluuding cylinder 110.

In the event that the weight tending to cause rotation of the platform at the time of failure of the main'control cylinder 1101s at the left of the center of the platform, as seen in FIGURE 5,; piston 128'will be pulled to the right by chain 122. This necessitates that "the fluid pass through the relief valve 134 following which time it readily passes through the check valve 136. As the fluid passes through the valve 136, a ball similar to that labeled 62 in FIGURE 4 is unseated while, as fluid passes through the relief valve 134, a sleeve similar to sleeve 'of FIGURE' L is retracted against-the pressure exerted Obviously, many modifications and variations may be ,made without departing from the spirit and scope of this invention, and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. A safety apparatus for platform hinged at one end thereof to a boom capable of being angularly raised and lowered from a support therefor comprising:

, (a) a first hydraulic cylinder-piston-piston rod assembly pivoted at one end thereof to said boom and at the other end thereof to aid platform, said assembly being pivoted to said platform at a point normally vertically displaced from the point at which said platform is hinged to said boom whereby to provide means for varying the angle between said boom and said platform and for maintaining said platform in a horizontal orientation;

(b) means for preventing sudden change in the angle described by said boom and said platform on failure of said first hydraulic cylinder-pi ton-piston rod assembly, said means comprising a second hydraulic cylinder-piston-piston rod assembly pivoted at one end thereof to said boom and at the other end thereof to said platform, said assembly being pivoted to said platform at a point normally vertically displaced from the point at which the said platform is hinged to said boom;

(0) an hydraulic fluid line connecting the piston side i of the cylinder of said second assembly and the rod side of the cylinder of said assembly;

(d) and a valve in the said line, said valve being set to prevent the flow of hydraulic fluid from the one side of said second assembly to another side of said second assembly except on application of pressure in excess of that represented by the weight of the said platform and its normal load when said platform is in use.

2. A safety apparatus for a platform having four walls extending upwardly therefrom to form a basket pivoted at one side thereof to a boom capable of being angularly raised and lowered from a support therefor comprising:

(a) a first hydraulic cylinder-piston-piston rod assembly pivoted at one end thereof to said boom and at the other end thereof to a wall of said platform, said assembly being pivoted to said wall at a point vertically displaced from the point at which said platform is hinged to said boom whereby to provide means for varying the angle between said boom and said platform and for maintaining said platform in a horizontal orientation;

(b) means for preventing a sudden change in the angle described by said boom and said platform on failure of said first hydraulic cylinder-piston-piston rod assembly, said means comprising a second hydraulic cylinder-piston-piston rod assembly pivoted at one end thereof to said boom and at the other end thereof to the said wall whereon the said first assembly is pivoted, said second assembly being pivoted at a point vertically displaced from the point at which the said basket is pivoted to the said boom;

(0) an hydraulic fluid line connecting the piston side of the cylinder of said second assembly and the rod side of the cylinder of said assembly;

(d) and a valve in the said line, said valve being set to prevent the flow of hydraulic fluid from one side of said second assembly to the other side of said second assembly except on application of pressure in excess of that represented by the weight of the said basket and its normal load when said basket is in use.

i 3. A safety apparatus for a platform having four walls extending upwardly therefrom to form a basket pivoted at one side thereof to a boom capable of being angularly raised and lowered from a support therefor comprising:

(a) a first hydraulic cylinder-piston-piston rod assembly pivoted at one end thereof to said boom and at the other end thereof to a wall of said platform, said assembly being pivoted to said wall at a point normally above the point at which said platform is hinged to said boom whereby to provide means for varying the angle between said boom and said platform and for maintaining said platform in a horizontal orientation;

(b) means for preventing a sudden change in the angle described by the said boom and said platform on failure of said first hydraulic cylinder-pistonpiston rod assembly, said means comprising a second hydraulic cylinder-piston-piston rod assembly pivoted at one end thereof to said boom and at the other end thereof to the said wall of the said platform whereat the said first assembly is pivoted, said second assembly being pivoted to said well at a point normally above the point at which the said first assembly is pivoted to the said boom;

(c) an hydraulic fluid line connecting the piston side of the cylinder of said second assembly and the rod side of the cylinder of said assembly;

(d) and a valve in the said line, said valve being set to prevent the flow of hydraulic fluid from the one side of said second assembly to the other side of said second assembly except on application of pressure in excess of that represented by the weight of the said basket and its normal load when said basket is in use.

4. A safety apparatus for a platform having four walls extending upwardly therefrom to form a basket pivoted at one side thereof to a boom capable of being angularly raised and lowered from a support therefor comprising:

(a) a first hydraulic cylinder-piston-piston rod assembly pivoted at one end thereof to said boom and at the other end thereof to a Wall of said platform, said assembly being pivoted to said Wall at a point vertically displaced from the point at which said platform is hinged to said boom whereby to'provide means for varying the angle between said boom and said platform and for maintaining said platform in a horizontal orientation;

(b) means for preventing a sudden change in the angle described by said boom and said platform on failure of said first hydraulic cylinder-piston-piston rod assembly, said means comprising a second hydraulic cylinder-piston-piston rod assembly pivoted at one end thereof to said boom and at the other end to the said Wall whereon the said first assembly is pivoted, said second assembly being pivoted at a point vertically displaced from the point at which the said basket is pivoted to the said boom;

(c) an hydraulic fluid line connecting the piston side of the cylinder of said second assembly and the rod side of the cylinder of said assembly;

(d) a valve in said line, said valve being set to prevent the flow of hydraulic fluid from one side of said second, assembly to the other side of said second assembly except on application of pressure in excess of that represented by the weight of the said basket and its normal load when said basket is in use;

(e) and a reservoir for hydraulic fluid in communication With the said line, the interior of said reservoir being under a superatmospheric pressure when the said reservoir is filled to a maximum extent and being under a pressure no less than atmospheric when the said boom is elevated to a maximum extent and the rod of the said second assembly extended to a maximum extent. a

5. A safety apparatus for a platform hinged at one end thereof to a boom capable of being angularly raised and lowered from a support therefor comprising:

(a) means for varying the angle between said boom and said platform and for maintaining said platform in a horizontal orientation;

(b) means for preventing a sudden change in the angle a i r a described by said boom and said platform onfailure of said first means, said meanscomprising an hydr-aulic .cylinder piston-piston rod assembly pivoted at one end to said boom and at the other end thereof 'to said'platform, said assembly being pivoted to said platform at a point normally vertically displaced from the point at which the said'platform ishinged to said boom; 7 I a p (c) an hydraulic fluid line connecting the of the cylinder of said assembly and the rod side of the cylinder of said assembly;

(d) and a valve in the said line, S d Valve fi to prevent the flow of hydraulic fluid from the one sideof said assembly to another side of said assembly except on application of pressure in excess of that represented by the weight of the said platform and its normal load when said platform is in use.

6. Safety apparatus for a platform hinged to a boom' 7 and capable of being angularly raised and lowered from piston side draulic cylinder-piston-piston rod assembly having,

means connecting the said assembly to the said platform and to the said boom; 7

(c) an hydraulic fluid line connecting oneside of the piston of the cylinder of said assembly and the other side of the piston of the cylinderrof said assembly;

(d) and a valve in the said line, said valve being set to prevent the flow of hydraulic fluid fromthe one side of said assembly to the other side of said assembly exceptyon application of pressure in excess of that represented by the rotational momentof the said platform and itsrmaximum normal loadwhen;

said platform is in use. a V 7. Safety apparatus for a platform hinged beneath the bottom thereof to a boom, said boom being capable of being angularly raised andlowered from a supportthere for comprising: r

(a) means for varying the angle between said boom and the said platform and forlmaintaining the said platform in a horizontal orientation; V (b)- means for preventing a sudden change in the angle described by said boom and said platformon failure of said first means, said' means comprising an hydraulic cylinder-piston-piston rod assembly, [said as sembly incluing a cylinder fixedly secured to the said platform and having a piston fitted'with a rod on either side thereof, a sprocket fixed against rotary motion relative to the said boom on the end-of said boom supporting said platform anda chain connecting each piston rod and trained aboutithe said sprocket; V (c) an hydraulic fluid line connecting either side of the, said cylinder on eitherside of the said piston thereof; c (d) and a valve in the said line, said valve being; set

bly except on application of' pressure in excessaof that represented by the rotational moment of the a being angularly raised and lowered from a support there-. for comprising: a 1

(a) means for varying the angle betweensaid boom and the said platform and for maintaining thejsaid platform in a horizontal orientation; 7 t

a v (b). .meanstfor'preventing a sudden change in the angle 1 to prevent the flow of hydraulic fluid from theone described by said boom and said platform on failure of said first means, said means comprising an hyhraulic cylinder-piston-piston rod assembly, said assembly including a cylinder fixedly secured to the said platform and having a piston fitted with a rod on either side thereof, a sprocket fixed againstrotary motion relative to the said boom on the end of said boom supporting said platform anda chain connecting, each piston rod and trained about the said 7 sprocket; V r r (c) an hydraulicgfluid line connecting either side of the said cylinder on either side of the said piston thereof; t a '(d) a valve in the said line, said valve being set to prevent the flow of hydraulic fluid fromthe one side of said assembly to another side of said assembly except on application of pressure in excess of that represented by the rotational moment of the said platform and its maximum normal load when said platform is in use; (e) and an idler sprocket mounted for rotation upon the said platform opposite the end of each of the "said piston rods, said chain being trained'about said idler sprockets. I 9. Safety apparatus fora platform hinged beneath the bottom thereof to a boom, said boom being capable of being angularly raised and lowered from a support therefor comprising: Y

I (a) means for varying the .angle betweensaid boom and the said platform and for maintaining the said platform in a horizontal orientation; (b) means for preventing a sudden change in the angle described by said boom and said platform on failure, of said first means, said means comprising an hydraulic cylinder-piston-piston rod assembly, said assembly including a cylinderfixedly secured to the said platform and having a piston fitted with a rod on either side thereof, a sprocket fixed against rotary motion relative to the said boom on the end of said boom supporting said platformand a chain connecting each piston rod, and trained about the said sprocket; i ('c) an hydraulic fluid line connecting either side of the said cylinder on either side of thesaid piston thereof; (d) and a pair of relief valves in the said line, each of said'valves being positioned to permit the flow of hydraulic fluid in one direction only from one side of the said assemblyto the other side of the Said assembly and prevent-ing flow of fluid except on application of pressure in excess of that represented by the rotational moment ofthe said platform and its 1maximum normal load when said platform is in use, each of the said relief valves being provided t with a series-mounted check valve, each of said check valves permitting flow of fluid only in the direction opposite to the direction of fluid flow permitted by the corresponding relief valve. g 10. Safety apparatus for a platform hinged beneath the bottom thereof to a boom, said boom being capable of being angularly raised andlowered from a support therefor comprising: (a) a first hydraulic cylinder-piston piston'rod assembly pivoted at one :end thereof to the said boom and at the other end thereof to said platform, whereby to provide means for'varying the angle between said boom andjsaid platform and for maintaining said i :platformin a horizontal orientation; (b) means for preventing a sudden change in the angle described by said boom and said platform on failure hydraulic, cylinder-piston-piston,rod assembly, said assembly including a cylinder fixedly secured -to the said platform and having a piston fitted with a rod on either side thereof, a sprocket fixed against rotary motion relative-to the said boom on-the end of said of said first means, said means comprising a second 9 16 boom supporting said platform'and a chain connectmoment of the said platform and its maximum ing each piston rod and trained about the said norm l load when said platform is in use. sprocket; (c) an hydraulic fluid line connecting either side of R f r n s Cited by the Examine! the last-mentioned cylinder on either side of the said 5 UNITED STATES PATENTS piston thereof;

((1) and a valve in the said line, said valve being set 2,606,073 3/52 Brock to prevent the flow of hydraulic fluid from the one 3,0 5,710 5/ 62 P0111 212-39 side of said last-mentioned assembly to another side 3,078,949 2/63 Hoard 182-2 of said assembly except on application of pressure 10 in excess of that represented by the rotational HARRISON MOSELEY, Primary Examllwr- 

6. SAFETY APPARATUS FOR A PLATFORM HINGED TO A BOOM AND CAPABLE OF BEING ANGULARLY RAISED AND LOWERED FROM A SUPPORT THEREOF COMPRISING; (A) MEANS FOR VARYING THE ANGLE BETWEEN SAID BOOM AND SAID PLATFORM AND FOR MAINTAINING THE SAID PLATFORM IN A HORIZONTAL ORIENTATION; (B) MEANS FOR PREVENTING A SUDDEN CHANGE IN THE ANGLE DESCRIBED BY SAID BOOM AND SAID PLATFORM ON FAILURE OF SAID FIRST MEANS, SAID MEANS COMPRISING AN HYDRAULIC CYLINDER-PISTON-PISTON ROD ASSEMBLY HAVING MEANS CONNECTING THE SAID ASSEMBLY TO SAID PLATFORM AND TO SAID BOOM; (C) AN HYDRAULIC FLUID LINE CONNECTING ONE SIDE OF THE 